Stacked heat interchanger



L. D. GUTHRIE sTAcxED HEAT INTERCHANGER Feb. 23, 1965 Fiied Maron 27. 1961 INVENTOR.

LYLE D. GUTHRI E 3,170,51 l Batented Feb. 23, 1.965

3,170,511 STACKED HEAT NTERCHANGER Guthrie, 1619 `Guy St., Apt. 3, San Diego, Calif.

Filed Mar. 27, 1961, Ser. No. 98,534 4 Claims. (Cl. 16S-10S) Lyle D.

This invention relates to a heat exchanger, and more particularly to a heat exchanger of the stacked heat-interchanger type.

Background One of the most satisfactory methods of heating fluids is to use the hot gases resulting from combustion, and to extract heat therefrom and transfer the heat to the fluid by means of heat-interchangers.

Since the results of combustion are hot gases, and the 'luids to be heated may be either liquids or gases, the following terminology will be used for clarity of explanation. The hot gases will be called flue gases, and the fluid to be heated will be called waten These terms however, should not be construed as meaning that my invention is limited to the heating of water.

Heat exchangers inherently have a number of problems. Amongthese are the tendency for water vapor in the line gas to produce corrosive action. Another problem stems from the necessity of obtaining the maximumy amount of heat from Ithe gases before they escape up the flue. This latter vproblemi requires that the heat interchangers have a large area, so that they are exposed to a large volume of hot flue gases, and can quickly extract a large amount of heat therefrom.

It however, a series of heat exchangers are sequentially presented to the flue gases, the cooled gases transfer only a small amount of heat to the rearmost heat interchangers.

Objects and drawings same amount of heat from the hue gases, even though the gases are relatively cooler when they pass the rearmost heat interchangers. v l n Y It is still another object of my invention to provide' an improved, novel heat exchanger that "is extremely efficient and easy to assemble. n p g The attainment of these objects and others will be realized from the following speeicationtaken in con- 'junction with the drawings, of Which- FIGURE l shows my 'basic inventivev concept; and FIGURES'Z-Llshow 'cross sectionsof the heat interchangers used therein.V Y.

Broadly speaking, my invention contemplates a heat exchanger comprising threesubstantially'concentric tanks;

The water to be 4heated is containedv in the innermostf portions of the flue gases. This tends to equalize the quantity ofheat transfer, that is the actual B.t.u. transfer, and therefore tends to equalize temperatures along the length of the stacked assembly, particularly at the juncture of the heat interchanger and the heated chamber. This results in decreased stresses, and therefore longer useful life for the equipment.

heated tank and in the outermost storage tank, while* the heating gases pass throughthe intermediate heater chamber. Heat interchangers are placed in the heater chamber in av stacked manner to sequentially extract heat from the flue gases, and to transmit the 4extracted heat toboth the heated chamber and to the storage chamber. The sequentially positioned heat interchangers have varies with lvane areas becoming progressivelylarger as'the flhe gases become progressivelyA cooler. This progression of vane areas providesv more efficient heat extraction from the progressively cooler flue gases. v 1 Y.

.i It will beirealized from the following description of my inventiom that the disclosed heat `interchangers have a .l

greater capabilitytor heat extraction from the cooler .The invention In the heat exchanger 10 of FIGURE 1, cold water flows through inlet pipe 12 into storage chamber 14. This comprises a tank of any desired conguration, wherein walls 16 have suitable construction and thermal insulative properties. If desired, a composite wall of strong material and an insulating liner may be used.

The cold water at the bottom of storage tank 14 as shown by arrow 1S, and enters the innermost heated chamber 20. The heated chamber is formed by a pipe 22, through which the water flows upwards as it is heated. (The heating process will be described later in greater detail.) The heated water emerges from the top of heated chamber Ztl asshown by arrow 24, and enters storage chamber 14.

As the heated water enters the top of the storage chamber, it may be withdrawn through the hot water outlet 26 as needed. `While the illustrationl shows the heated water to rise through the heated chamber and pass into the storage chamber by Vconvection and gravity flow, my invention will also operate in a horizontal position, although a pump may then be required.

In order to heat the water, fuel gas flows through fuel line 28 at the bottom of the heat exchanger, and enters burner 3i). Here the fuel gas is burned, and the hot gases of combustion-flow upwards through the heating chamber 32 formed by walls 33' and pipeV 22, and out of the flue 34. While a gas burner 30 is shown, it may of course be replaced by an oil burner, electric heater, steam, or any other source of heat. n

As the hot flue gases travel along heating chamberl, it is necessary to extract the heat from them and to transfer the extracted heat to the water. I accomplish this in a manner which will now be explained in some detail.

As may be seen from FIGURE l, I use a plurality of stacked heat interchangers .36 positioned sequentially along the flow path of the hue gases. The heat interchangers are grouped into three stages. The vlirst stage has four identical heat interchangers, 36A-36D; the second stage also has four identical heat interchangers 36E- 36H; and the third stage has three heat interchangers Lidl-36K. n f

The heat interchangers 36 comprise'an upper band 38 and a lower yband dit, these bands being interconnected In one arrangement, lower band d@ isbonded to wall. 343, while in another arrangement lower band 4t) merelyA In the latter arrangement, an`

presses against wall 33. expansion opening 44 is used.

' Operation` As thevhot gases from burner Si) pass the iirst heat interchanger 36A, they heat varies 42A. These conduct heat`r to upper band 38A and lower band @A; .these in .turn heating walls 22 and 33 respectively. Each of these wallsjsin contact with water; so rthat the water in heatedn l chamber Zit andin storage chamber 14 is heated simulfV taneouslyL l Y Y v Since the hot ilue gases heat therst heat interchanger 36A, it follows that thegases are Vpooled somewhat during this process. 1Asaresult, the lue gases are some-l ilows What cooler wheny they reach-an intermediate stage heat v interchanger, such as 36E.

In order tocornpensate for the presence of the somewhat cooler flue gases surrounding it, lheat interchanger 35E hasmorevatnes than the rst stage heat vinterchanger. Y.

Thisrneans that the intermediate stage heat inerchanger 36E is slightly more eilicient, but since it is in an atmosphere. -of cooler ue gases, the overall heat extraction isv about the same as that of the first stage heat interchanger.

By the time the iiue gases. reach the third stage heat Vinterchanger 36], the gases are'even cooler than previously. Irl-accordance with my inventive concept, the heat interchanger Sl'fhas more-vanes than heat interchanger' In this way, kheat interchanger 35] extracts substantially: the same `amount of heat, despite the fact` that it is surroundedby reiativelycool line gases.- Y It'is 'known :that if the line gases drop below lthe socalled critical temperature ot about 90 degrees Fahrenheit, the moisture vapor contained thereintends to con- `d`ense. .The condensation absorbs chemicals from the yiiue gases, and forms corrosion producing deposits.

To avoid this possibility, the flue gases should not cooledfbelovv 90 degrees Fahrenheit. The temperature of the exhaust may be readily controlled by using .a predetermined number of` heat interchangers having givenv number .of vanes. n y

' Since the iinal stage heat interchangers have the largest number of`vanes, and therefore tend .to introducethe largest impedance tothe tiovv ot the flue gases, it may beV desirable at times, to have fewer heat interchangers in the iinal stage than in preceding stages.

` In FIGURES 2 4, there are yshown, cross sectional viewsfot heat interchangers .thatare typical Vof the threeV stages. As shown in FIGURE n*2, the iirst stage lheat interchanger 36B has an .upper band 38B` encircling inner pipe V22. Six vanes 42B connect vthe upper band 33B with lower banddtB, which is in contact With Wall 33. FIGURE Y3 'shows a secondV stage heat interchanger v 36E. It comprises the same basic Vparts as .the earlier can. .be used to selectively control the .direct-ion. and.

` with the opening in wall 33. At this time the inlet opening of the heated chamber 'also coincides WithV the corresponding opening of Wall 33.

The walls forming the common openings maythen be sealed..

through the tine, to escape.

When using this arrangement, lower bands Lit) .are eithenopenedwide initially, or expand when heated, in order to make goodv heat conducting contact with the inner surface of Wall 33. i

In the previously discussed embodimentl where` lower bands ltil'are bonded to walls 33, heat losses occur when' burnerk ifis turned off. At that timethe hot Water in storage. chamber 14 heats. the lov/erbands. di?, and these heat vanes 42. These vanes in turn heat the air in the now-'unused heating. chamber, and` the lheated air rises In therernbodirnent whereinlover bands 4? are not bonded to vWalls 33, these bands contract when .the burner ris turned off. .The heat transmittingV contact between lower bands'iiltand Walls 33 is thus broken, to obviate heating the air Vinthe heating chamber. In this way, heat losses are minimized.` v l n Heat transfers .more eicientlyto uids-in movement and to therlowest temperatured fiuid Within a chamber. This` structure utilizes thesev two natural laws by'concentratingy the-greatest portion .of heat onto the reduced stage hea-t interchangen except vthat it has eight vanes 42E to extract heat from the cooler `tlue gases that surround it. g

FIGURE-4 shows a still later-stage; heat interchanger 361 It will be'seen that this heat interchanger also contains the same basic parts as theA others, Yexcept that itY has twelve vanes 42. vIn this Way, each heat interchangerv v extracts substantially the same arnountof heat from the ue gases. Y

amount of Waterin theinner chamber vby use of Varies thatV direct their heatto'the inner tube. When lthe heat is absorbed bythe. Huid, it expands, becomes lighter, moves upwardrwithin the inner chambergand .out into Y the storage chamber; Whereasthe heavier colder Water Heat interchangers-SS maybe readily formed from at sheet lmetal by a stamping operation.V The trapezoidally shaped areas .are first ,punched out, the bands. and flanges.V l are given thenecessary angular'relation, andthe resultar stamping isthen rolled tothe desired conicalform.

'f Vm'ins y The three-'stagevheat exchanger lil of FIGURE 1 has.

the advantage that. each stage uses a number of identical heat interchangers'36.

heat-interChanger. Thelheatiinterchangers transmit heat' v terchangersY are easily-made. l. The` heat .absorbing areas Alternatively, instead off using stages, .each successiveV heat interchanger may have' progressively more evanes;

or may have the same number of vanes, each having a,`

slightly larger area. It may be desired, at times, to vary both'rthe 'number andthesize of the-vanes in orderto have equally overall-efficient heat extraction steps.

Under some conditions it may bedesirable to transmit more heat to the heatedchamber 2i) than tothe stor- Vage chamberlft. 'Ihis'resultis readily achievedrinanyof A a `plurality `ot Vways. For example, Ythe Widths Riot Y vbandsv 38 and 4d can .be adjusted,v theheat conducting characteristics between" Walls Zland '33 and the handsicanbe modified; and theshape fof the vanes can be 'con'- Y trolled.'O Any one or al combination of Lthesel parameters.

movesinto the inner chamber, thereby creating a-selfinduced yrapid movement ofthe fluid. The incoming coldesttemperatured iiuid isthus subjected to the greatest concentration Vof heat.

A dvantages My heatexchanger has.; several advantages over priorart devices. y n

E It provides substantially equal heat extraction for each in both directions Vto the storagev chamber andthe heated chamber. The" amount of heattransmitted in'each direction can fbe leasily)l controlled.V The individual heat inhave' been greatly 'increased tand-.,thereforef the overall length of the heat exchanger-maybe .greatly decreased kin length, and a long. flue is no longer necessary. And finally, the unit. is easilyiassembled. Y

"It vis understood that'minor4 variation from the form f of the invention disclosed herein may be made with-V Vout departure from the spirit and scope-of the invention, and vthat f the specication land drawingr are 4to be; considered asf-merely illustrative` rather than-limiting.

heat'exchangerV comprising: g Y v Y -threeconcentric enclosures, said tirst-encliosure cornprising a-pipethat formsya heatedcharnber, the Vspace` Y .betweenisaid tirstandvsecond enclosures formingI ay l f heatercharnber, andthe kspace between-saidv second Yand third enclosuresforming ak storageichainber; f s.

n means forformingapassage.betiveenfone end'of said` heated chamber and one end of said storage chamber;

means for forming a passage between the other end of said heated chamber and the other end of said storage chamber, whereby fluid may pass from said storage chamber into said heated chamber to be heated and may then pass from said heated chamber to said storage chamber to be stored until Withdrawn;

a plurality of heat interchangers, each having an inner band, an outer band, and generally radially extending vanes interconnecting said bands; the inner band of each interchanger being axially spaced relative to the outer band;

means for positioning said heat interchangers in a stacked manner along the length of said heat exchanger with said inner bands in heat conducting relation with said inner enclosure, said outer bands in heat conducting relation with said second enclosure, and said vanes positioned in said heater chamber, the vanes of successive heat interchangers having progressively larger areas along substantially the entire length of said heater chamber, whereby successive vanes are enabled to more efficiently extract heat from the passing gases;

and means for causing hot flue gases to traverse said heater chamber, and cause said vanes to extract heat from said flue gases and to transmit said heat to said heated chamber and said storage chamber.

2. A heat exchanger comprising:

three concentric enclosures, said first enclosure comprising an elongated pipe that forms a heated chamber, said second enclosure, comprising an elongated pipe that terminates in a flue, and said third enclosure comprising an envelope, the space between said first and second enclosures forming a heater chamber, and the space between said second and third enclosures forming a storage chamber;

means for forming a passage between one end of said heated chamber and one end of said storage chamber; means for forming a passage between the other end of said heated chamber and the other end of said storage chamber, whereby fluid may pass from said storage chamber into said heated chamber to be heated, and may then pass from said heated chamber to said storage chamber to be stored until withdrawn;

a plurality of heat interchangers, each having an inner band, an outer band, and generally radially extending vanes interconnecting said bands; the inner band of each interchanger being axially spaced relative to the outer band;

means `for positioning said heat interchangers in a stacked manner along the length of said heat exchanger with Ithe inner surface of said inner band in heat conducting relation withk the outer surface of said inner enclosure, said outer surface of said outer bands in heat conducting relation with said inner surface of second enclosure, and-said vanes positioned in said heater chamber, the vanes of successive heat interchangers having progressively larger areas, whereby successive vanes are enabled to more eiciently extract heat from the passing gases;

means for causing hot flue gases to traverse said heater chamber and said tlue, and cause said vanes to extract heat from said flue gases and to transmit said heat to said heater chamber and said storage charnber;

means for introducing a fluid to be heated into said storage chamber;

and means for withdrawing heated tluid from said storage chamber.

3. The combination of claim 2 wherein said larger areas of said vanes comprise additional vanes.

4. The combination of claim 2 wherein said larger areas of said vanes comprise the same number of larger area vanes.

References Cited in the tile of this patent UNITED STATES PATENTS 900,303 Panasevitch oct. 6, 190s 1,148,865 Shipman Aug. 3, 1915 1,616,143 Schnepp Feb. l, 1927 1,637,682 Clarkson Aug. 2, 1927 2,638,889 Dow May 19, 1953 FOREIGN PATENTS 17,909 Great Britain of 1902 444,150 Great Britain Mar. 16, 1936 766,665 France Apr. 16, 1934 

1. A HEAT EXCHANGER COMPRISING: THREE CONCENTRIC ENCLOSURES, SAID FIRST ENCLOSURE COMPRISING A PIPE FORMS A HEATED CHAMBER, THE SPACE BETWEEN SAID FIRST AND SECOND ENCLOSURES FORMING A HEATER CHAMBER, AND THE SPACE BETWEEN SAID SECOND AND THIRD ENCLOSURES FORMING A STORAGE CHAMBER; MEANS FOR FORMING A PASSAGE BETWEEN ONE END OF SAID HEATED CHAMBER AND ONE END OF SAID STORAGE CHAMBER: MEANS FOR FORMING A PASSAGE BETWEEN THE OTHER END OF SAID HEATED CHAMBER AND THE OTHER END OF SAID STORAGE CHAMBER, WHEREBY FLUID MAY PASS FROM SAID STORAGE CHAMBER INTO SAID HEATED CHAMBER TO BE HEATED AND MAY THEN PASS FROM SAID HEATED CHAMBER TO SAID STORAGE CHAMBER TO BE STORED UNTIL WITHDRAWN; A PLURALITY OF HEAT INTERCHANGERS, EACH HAVING AN INNER BAND, AN OUTER AND GENERALLY RADIALLY EXTENDING VANES INTERCONNECTING SAID BANDS; THE INNER BAND OF EACH INTERCHANGER BEING AXIALLY SPACED RELATIVE TO THE OUTER BAND; MEANS FOR POSITIONING SAID HEAT INTERCHANGERS IN A STACKED MANNER ALONG THE LENGTH OF SAID HEAT EXCHANGER WITH SAID INNER BANDS IN HEAT CONDUCTING RELATION WITH SAID INNER ENCLOSURE, SAID OUTER BANDS IN HEAT CONDUCTING RELATION WITH SAID SECOND ENCLOSURE, AND SAID VANES POSITIONED IN SAID HEATER CHAMBER, THE VANES OF SUCCESSIVE HEAT INTERCHANGERS HAVING PROGRESSIVELY LARGER AREAS ALONG SUBSTANTIALLY THE ENTIRE LENGTH OF SAID HEATER CHAMBER, WHEREBY SUCCESSIVE VANES ARE ENABLED TO MORE EFFICIENTLY EXTRACT HEAT FROM THE PASSING GASES; AND MEANS FOR CAUSING HOT FLUE GASES TO TRAVERSE SAID HEATER CHAMBER, AND CAUSE VANES TO EXTRACT HEAT FROM SAID FLUE GASES AND TO TRANSMIT SAID HEAT TO SAID HEATED CHAMBER AND SAID STORAGE CHAMBER. 